The disclosure of Japanese Patent Application No. 2002-011846 filed on Jan. 21, 2002 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to an electromagnetic valve controller for controlling electromagnetic valves each functioning as an intake valve or an exhaust valve of an internal combustion engine.
2. Description of Related Art
An internal combustion engine in which intake valves and exhaust valves are each formed by an electromagnetic valve is known in the art. Such an internal combustion engine is disclosed in, e.g., Japanese Patent Laid-Open Publication No. 2000-257481. In such an internal combustion engine, intake valves and exhaust valves can be driven with greater flexibility as compared to an internal combustion engine in which intake valves and exhaust valves are driven by a cam mechanism. Therefore, an internal combustion engine having electromagnetic valves is capable of implementing operations such as a single-valve operation, a reduced-cylinder operation, and a six-strokes per cycle operation (hereinafter, referred to as xe2x80x9csix-cycle operationxe2x80x9d). The single-valve operation is operation in which one of two intake valves provided in each cylinder is stopped. The reduced-cylinder operation is operation in which at least one of the cylinders is stopped. The six-cycle operation is operation in which the four strokes conducted in four-strokes per cycle operation (hereinafter, referred to as xe2x80x9cfour-cycle operationxe2x80x9d) are conducted in six strokes of the piston. If the single-valve operation, the reduced-cylinder operation, the six-cycle operation, and the like (hereinafter, these operations are collectively referred to as xe2x80x9cvalve-stopped operationxe2x80x9d) are conducted under appropriate conditions, fuel consumption of the internal combustion engine can be improved. Therefore, internal combustion engines of this type having electromagnetic valves may exhibit excellent fuel consumption characteristics as compared to a commonly used internal combustion engine which activates the intake valves and the exhaust valves by a cam mechanism.
While valve-stopped operation is conducted in the internal combustion engine having electromagnetic valves, lubricating oil may disadvantageously accumulate within the stopped electromagnetic valve. If the internal combustion engine is stopped in this state, the electromagnetic valve which is in the stopped state when the internal combustion engine is stopped may operate less smoothly than the electromagnetic valve which is in the operating state when the internal combustion engine is stopped.
If the internal combustion engine is restarted in such a state and a request such as an acceleration request is generated while the internal combustion engine is being held in such a state, a failure such as step-out is likely to occur in the electromagnetic valve that operates less smoothly. Therefore, if valve-stopped operation is conducted in internal combustion engines of this type having electromagnetic valves, it is desirable if a state in which all of the electromagnetic valves can operate smoothly is established immediately after the internal combustion engine is started.
One function of the above conventional internal combustion engine is to conduct initial suction of all of the electromagnetic valves and then start the starter when a request to start the internal combustion engine is generated. This function is directly intended to disperse the power required for the initial suction of the electromagnetic valves and the power required to drive the starter. However, the above function enables all of the electromagnetic valves to be operated before the internal combustion engine is started. In other words, even if there is an electromagnetic valve which operates less smoothly upon starting of the internal combustion engine, such an electromagnetic valve is operated before the starter is started. Therefore, this internal combustion engine can improve operation characteristics of the electromagnetic valves even if there is an electromagnetic valve which operates less smoothly upon starting of the internal combustion engine. In this respect, the above conventional internal combustion engine is expected to demonstrate a degree of effectiveness in preventing a failure of an electromagnetic valve caused by execution of valve-stopped operation.
As described above, however, the above conventional internal combustion engine conducts initial suction of all of the electromagnetic valves before starting the starter. More specifically, the above conventional internal combustion engine is not started until initial suction of all of the electromagnetic valves is completed after a request to start the internal combustion engine is generated by a driver of a vehicle. In other words, the time required to start the internal combustion engine is long enough to cause displeasure for the driver. Therefore, the control method used in the above conventional internal combustion engine is not always appropriate as a method for preventing a failure caused by the execution of valve-stopped operation.
The invention is intended to solve the above problems, and it is an object of the invention to provide an electromagnetic valve controller capable of appropriately preventing a failure of an electromagnetic valve due to execution of valve-stopped operation, without degrading starting response characteristics of an internal combustion engine.
In order to achieve the above object, according to an aspect of the invention, a controller of a plurality of electromagnetic valves each functioning as an intake valve or an exhaust valve of an internal combustion engine, comprising a valve control portion that controls the electromagnetic valves in one of a normal operation mode and a valve-stopped operation mode, the normal operation mode being a mode in which all of the electromagnetic valves are controlled in order to implement the four-cycle operation of the internal combustion engine, and the valve-stopped operation mode being a mode in which at least one of the electromagnetic valves can be regarded as being stopped as compared to the normal operation mode, wherein the valve control portion inhibits control in the valve-stopped operation mode for a predetermined period after the internal combustion engine is started.
The invention having the above structure provides the following effects. Control in the valve-stopped operation mode is inhibited for the predetermined period after the internal combustion engine is started. Therefore, all of the electromagnetic valves can be operated during the predetermined period. As a result, according to the invention, it is possible to render all of the electromagnetic valves into a state where they can operate smoothly during this predetermined period, without degrading starting response characteristics of the internal combustion engine.